1. Field of the Invention
The present invention relates to a lens unit including a lens array, a light-exposure apparatus including the lens unit, and an image forming apparatus including the light-exposure apparatus.
2. Description of the Related Art
A light-emitting diode (LED) print head is employed as a light-exposure apparatus (optical print head) of an image forming apparatus of an electrophotographic system (see, for example, Patent Document 1). The LED print head includes an LED array including a plurality of LEDs arranged on a board, a lens array including a plurality of lens elements (microlenses) for converging light emitted from the plurality of LEDs, and a lens holder for holding the board provided with the LED array and a lens unit including the lens array.
Patent Document 1 is Japanese Patent Application Publication No. 2013-15847.
The coefficient of linear expansion in a longitudinal direction of the lens array, however, is different from the coefficient of linear expansion in a longitudinal direction of the board provided with the plurality of LEDs, and thus, a temperature change causes a relative displacement between the plurality of LEDs (LED array) and the plurality of lens elements (lens array). This displacement changes an imaging state (the shape and amount of light forming an image on a photosensitive drum) of the LED array formed by the lens array, thereby causing banding (periodic vertical stripes) corresponding to a pitch of arrangement of the plurality of lens elements in a printed image.